Apparatus for slotting and cutting pipe



y 9 M. MUSKAT ET AL 2,684,030

APPARATUS FOR SLOTTING AND CUTTING PIPE Original Filed Sept. 11, 1945INVENTORS MORRIS MUSKTYI FLOYD w. PARK/RR lLLIfiM L- KEHL MATTORNEYPatented July 20, 1954 APPARATUS-EOR SLOTTING AND'T-CUT-TING PIPE MorrisMuskat, .Oakmont, Pa, Floyd W. .Parker, Harrogate,,,.Tenn.,.and WilliamL. Kehl, Penn Township, Allegheny County, Pa;, assignorsto- GulfResearch &- Development -Gompany,- Pittsburgh, Pa., a corporation ofDelaware Original application:- September: 11, 1945, SerialvNo..615,568... Divided amllthis applicationcNovember 25, 1949; SerialNo. 129,252

4 Claims:- 1?

This-invention concerns atnew-and useful appara-tus for cutting pipe;Which-apparatus is particularlyadvantageous for use in limited confinessuch-as Well bores. Inparticularitconcerns'ap: paratusfor employingspecially shaped and spee V cially disposed explosive charges .forcutting well casing.

This application a division'oi ourcopending application Ser; No.615,568, filed September 11,

entitled Apparatus, for Perforating and resultant effect of shaping the,high explosive.

charge so that its end provides a concave surface facing theobject to bepenetrated, and in which, moreover; this concave surface'is linedwith aninert-material such as a metal, ceramic or plastic.

Such shaped and lined charges. are very eifective increating holes insolid .objects including steel;

rock, cement; etc. The holes created areoi considerable depth anddiameter, although these may bevaried over an appreciable range byvarying the calibre of the explosive charge, its dis-v tribution andcomposition, the geometry of the. concave shaped'surface, thematerialand thick-v ness of the liner, and the standmftdistance be-V-tween the forward end ofthe. charge. and the target. We have utilizedthis eifect in the ap paratus of this invention useful for pipe-cuttingoperations in boreholes.

This invention is useful in cutting off well case ing. if it is'desiredto recover such casings aboveacemented portion. Heretofore expensivemechanical devices have been inserted into the Well on'a rotatable drillstem to out the casing around its, circumference. Ino-ld wells, havingno. drill ing equipment available, it has been common to use explosivesto break off the casing. Shootingj' the casing by meanspf ordinaryexplosives often results in spreadingof the broken end so that it issometimes :diflicult or impossible to pull thepipe out of the hole. Bytheuser-offourxinvention employing properly-shaped explosive charges; aclean circumferential cut is easily and quickly made. Itmay likewise beused for cut ting olf collars. between-strings of casings. The apparatusis also applicable to cutting off drill pipewhich has become stuck. tmay further be used for-cutting off any pipe; whether in the groundorabove the ground,- when conditions permit access only-to their-asidethereof I It: iseccording-ly an object of this -invention 'to provide animproved apparatus: for cutting: thecasing ofaborehole:

Another-obj ect ofthis invention is t0"13I-.OVldel apparatus forcuttingthe casing-of a borehole by.

' the useof a shaped high explosive-charge.

Another object of thisinventionis. to provide apparatus-Which achieves ahighly efiicient cuteting action through steel "or metal pipe.

Anothero-bj set of this invention I is to 1 provide amps-cutting meansemploying the-cuttin effect? of an explosive jet;

It is'also an object of thisinvention to provide a method of cuttingwell casing WhlCll-iS sub-'- stantiallyfree from the disadvantage offorming burrs onthe inside of-the casing around'the cut orslotma-detherein.

A still further object of this invention is to" provideapparatus forseveri-ng pipe -by the use =-of aspecially-shaped high explosive chargeAnotherobject of this invention-is to provide a means for severing pipeemploying the cuttingefiectofan explosive jet.

These and-otheruseful objects may be accom plished b ytheapparatus ofour invention clescrib'edin this specification, of which'theaccompanyingydrawings form a part; and inwhi-ch:

Figure 1' shows atop-plan'view, partly 'in section ofa form-oftheexplosive-cartridge useful forsevering pipe or casing;

Figure 2 shows-aside view of the form of explosive-cartrldge of Figure 1Figure '3 shows a longitudinal section of an ap paratus for cutting pipeby-means of-ashaped explosive charge; and

Figure shows a section of'the apparatus-taken along line AA'of Figure 3.

In'the apparatus of our invent-ionthe explosive is placed a certaindistance from the target, namely, the wall of the pipe; Theeifect of theexplosive is to createa cut or slot in the target by virtue of aspecially shapedand lined cavity in the surface of the explosive facing"the target. The target is notshattered; Virtually the whole penetratingpower of I the explosiveused arises from-theeiiect of the cavityplusliner formed in the surface-of the explosive facing the material tobe out; This fact is-apparently closely related to what-has beenpreviouslyknown'in the explosive artasthe' Munroe efi'ect. While thereare theories for this-effect; it basically represents purely anempirical discovery. The theory sug gests the-possibility'thatanexplosive'jet of very high velocity-is 'formed opposite the-cavity;and this j et "has a strong penetrating or cutting effect: Thenature'oithe'jet-maybecontrolled and its eihciency augmented by placinginert non-explosive material in the cavity as a liner.

The dimensions of the cut produced by a shaped explosive charge dependon the shape and the dimensions of the cavity; the kind, amount anddistribution of high explosive in the charge; the nature of theconfinement of the charge; the material, dimensions, and physicalproperties of the cavity liner; the distance between the base of thecavity and the surface of the target material; and the nature of thetarget material. By making proper selections of the above variables, thejet effect can be made to penetrate large distances into the targetmaterial.

The jet may be controlled by suitably varying other important parametersof the cavity liner, such as the included angle, liner material, linerweight, and stand-off from the target. It is true that an unlined cavitywill give approximately the same target hole volume as the lined cavity,but the depth of the penetration is very much greater with the linedcharge. The reason for this appears to be that the high explosive forms,from the liner material, a fine spray or jet which :has very highpenetrating power. The material of the cavity liner may be metallic, forexample, steel, aluminum, brass, lead, copper; or it may be ceramic; orglass; or of plastic composition. The cavity need not of necessity havea straightsided cross-section, but may be circular, parabolic, or mayhave other equivalent shapes.

Material of appreciable density within the cavity greatly diminishes thepenetrating action of the charge merely because it prevents formation ofthe jet. When any dense material is some distance from the base of thecavity it is equivalent to a corresponding amount of the target in thepath of the penetrating jet. In either case the residual penetration isgreatly reduced. Therefore, material of appreciable density, for examplewater, must be excluded from the cavity, since the presence of suchmatter within the cavity greatly diminishes the penetrating action ofthe cavity charge. Thus, for work in liquids, the base of the cavity isprovided with a suitable cover to prevent any liquid entering thecavity. The nature of the material surrounding the charge alsoinfluences the hole-formation performance considerably. An otherwiseunconfined charge in a well would effectively be confined by Y any fluidpresent in the well. Thus, if unconfined shots are to be made in afluid-filled well, the charges may be placed in a suitably-designedcontainer which prevents the fiuid from surrounding the charges.

The high explosive may be of any type such as pentolite, tetryl, TNT,etc, and may be augmented by any suitable chosen booster explosive. Forexample, tetryl could be used as a booster for pentolite, since theformer is more sensitive to shock than the latter. The choice of highexplosive material must be governed by the conditions under which it isto be used as is generally the case in any explosive application.

The apparatus encompassed by this invention makes use of linearwedge-shaped lined cavities to make linear cuts in the casing. Inparticular, to cut the casing around its circumference so as to permitpulling of the upper section, this apparatus uses a wedge-shaped linedcavity encircling a cylindrical stem of high explosive which may besolid or filled with a central inert core. On detonation of the highexplosive along its inner boundary a uniform cut will be produced in thecasing opposite the lined cavity. The

4. .wedge angle, the nature of the liner, and standoif of the cavityfrom the casing wall are chosen to fit the particular condition of theapplication.

Figures 1 and 2 show a lined cavity charge in which the cavity 50ext-ends circumferentially around the explosive charge 5!. The cavity 50is lined with lining material 52 and is closed by a cover 53. Detonationof the explosive is initiated at the center point 54 where there may bea small axial hole for inserting the fuse. Such a shaped charge may beemployed in an apparatus for cutting casing, such as shown in Figures 3and 4.

Figure 3 shows a longitudinal sectional view of a casing cutter in awell bore and Figure 4 is a transverse sectional view taken on the lineA-A of Figure 3. A ring-shaped explosive charge 30! containing aperipheral trough or cavity 302 is lined by a liner 303. Well fluids areprevented from entering the cavity 302 by the cylindrical cover 304which forms pressure-tight seals with upper plate 305 and lower plate305 by means of .gaskets 301 and 308. An axially-located metal .piece309 also makes pressure-tight seals with plates 305 and 306 by means ofgaskets 310 and 3! I. The section of the piece 300 lying between plates305 and 306 is enlarged and serves to prevent the collapse of theseplates when the cutter is subjected to high external pressure. The piece309 is attached to the lower plate 306 by means of the threads 3l2. Thelock ring 3&3 serves to secure the top 305 on piece 309. A plurality ofradial holes 3| 4 in the piece 300 communicate between the charge 301and an axial hole 3l5. The radial holes 314 and the portion of the hole315 near the radial holes 3| 4 are filled with explosive. An end plug3H5 is attached to the lower end of piece 309 by means of the threads 3|1, and forms a pressure-tight seal with piece 309 by virtue of gasket3|8. An electrically-actuated .detonator 310 is in contact with theexplosive contained in the hole 3l5. The lead wires 320 pass through thehole 315 to the fuze-chamber .32! which is attached to piece 309 bymeans of threads 322 and forms a pressure-tight seal with piece 309 byvirtue of gasket 323. A cable 32 attached to the chamber 32I is themeans of 2i5sing and lowering the cutter within the casing The assemblyof the casing cutter is accomplished in the following way: The plug 316is threaded into piece 309 and the latter into bottom plate 300. Theexplosive within piece 309 may be introduced at this time or previously.The ring-shaped charge 30L together with the liner 303, is then placedin position around the enlarged portion of piece 309 as is the cylinder304. The top plate 305 and the lock-ring 3E3 are then placed in positionand secured. The electric detonator 3l9 is then inserted into the bore3l5 so as to be in contact with the explosive, and the leads 320 areconnected to the fuzechamber 32I after which the latter is threaded ontothe upper end of piece 300.

The fuze-chamber 3 may contain mechanisms which arm and disarm thedevice under appropriate conditions, and a mechanism for locating theends of easing segments if it is desired to cut away the casing at anyfixed distance relative to a collar.

The operation of the device is as follows: When the cutter has beenlowered to the proper position in a well and when all arming devices inthe fuze-chamber have functioned, an operator on the surface sends anelectrical impulse to the detonator 3I9 by means of the cable 324 and abattery or other source of voltage at the surface. The detonation waveinitiated on the axis by the detonator is propagated through thechannels 3| 4 to the charge 31' which, on detonation, severs the casing325 along the plane AA.

The explosive may be any suitable high-explosive such as 50-50pentolite, and may be formed in any convenient manner such as casting orpressing. The annular region bounded by the cylinder 394, the liner 303and the plates 305 and 306 must be kept free of any dense matter of anykind. The cutting ability of the device depends on the shape, thickness,and material of the liner 303, the stand-01f distance measured from theoutermost position of the liner to the target, and the material of thetarget itself. We have discovered that the width of the charge 3!, i.e., the separation between plates 305 and 306 should be approximately 1to 3 times the combined thickness of the cylinder 304 and casing 325.

We have discovered that steel liners 303, Figure 3, having a cavityangle in the range of 80 to 140 and with thicknesses ranging from 0.02to 0.04 charge width are most satisfactory. The corresponding stand-offrange is preferably from 0 to 2 charge widths.

Liner 303, Figure 3, may alternatively be made of aluminum. In this casethe desirable cavity angle is in the range of 70 to 140 with thicknessranging from 0.04 to 0.10 times the charge width. The stand-01f mayrange from 0.5 to 4.0 times the charge width for best results, thelarger stand-offs being associated with the larger cavity angles.

We have shown the cutting charge liner to have a strictly angular cavityshape as drawn in Figures 1 to 4, but it may alternatively be parabolic,circular, or have other shapes. Furthermore, liners may be made ofmaterials besides steel or aluminum, these being cited merely by way ofexample. The liner of the cutting charge cavity may be any of the inertmaterials previously mentioned.

What we claim is:

1. Apparatus for cutting pipe comprising an explosive charge in theshape of anannular ring having an outwardly-directed cavity, anexplosion-confining annular lower plate in contact with the lower sideof said ring, an explosionconfining annular upper plate in contact withthe upper side of said ring, support means passing through the centralopenings of said ring and said plates supporting said plates in spacedrelationship, said support means having an axial channel and a pluralityof radial channels from said axial channel to the inner surface of saidring, an explosive in said axial channel and in said radial channels,and means for initiating detonation of said explosive in said axialchannel.

2. Apparatus for cutting pipe comprising an explosive charge in theshape of an annular ring having an outwardly-directed cavity, anexplosion-confining annular lower plate in contact with the lower sideof said explosive ring, an explosion-confining annular upper plate incontact with the upper side of said explosive ring, support meanspassing through the central openings of said explosive ring and saidplates supporting said plates in spaced relationship, detonating meansin said support means, and an explosivefilled channel leading from saiddetonating means to the inner surface of said explosive ring.

3. Apparatus for cutting pipe comprising an explosive charge in theshape of an annular ring having an outwardly-directed cavity, anexplosion-confining annular lower plate in contact with the lower sideof said explosive ring, an explosion-confining annular upper plate incontact with the upper side of said explosive ring, support meanspassing through the central openings of said explosive ring and saidplates supporting said plates in spaced relationship, a cover over thecavity of said explosive ring sealed against said upper and lowerplates, detonating means in said support means and an explosive-filledchannel leading from said detonating means to the inner surface of saidexplosive ring.

4. Apparatus for cutting pipe comprising an explosive charge in theshape of an annular ring having an outwardly-directed cavity, anexplosion-confining annular lower plate in contact with the lower sideof said explosive ring, an explosion-confining annular upper plate incontact with the upper side of said explosive ring, support meanspassing through the central openings of said explosive ring and saidplates supporting said plates in spaced relationship, a liner contiguousto the cavity of said explosive ring, a cover over the cavity of saidexplosive ring sealed against said upper and lower plates, detonatingmeans in said support means, and an explosivefilled channel leading fromsaid detonating means to the inner surface of said explosive ring.

References Cited in the file of this patent- UNITED STATES PATENTSNumber Name Date Re. 23,211 Mohaupt Mar. 21, 1950 2,399,211 Davis Apr.30, 1946 2,415,814 Davis Feb. 18, 1947 OTHER REFERENCES An article bySukharersky in a Russian publication, Voina i Tekhnika, volume 253 of1926, pages 18-24 and 6 sheets of drawings. (Copy in Div. 70.) Anunoficial translation of this article comprising 24 sheets of materialdrawings included is in Division 70.

A Scientific Approach to the Industrial Application of Shaped Charges,by Lawrence, in the Explosive Engineer, November-December, 1947, pages171-183. (Copy in Div. 70.)

